1. Field of the Invention
The present invention relates to a thermosetting silicon-containing antireflection film-forming composition to form a silicon-containing antireflection film used as an intermediate layer of a multilayer resist process used in a fine processing of a semiconductor device manufacturing and the like; a substrate having the silicon-containing antireflection film from the composition; and a patterning process using the same.
2. Description of the Related Art
With highly integrated LSI's providing highly increased speeds, finer pattern rules are being rapidly promoted. Commensurately with the fineness, the lithography technique has attained formation of fine patterns, by virtue of light sources of shorter wavelengths and resist compositions appropriately selected therefor. The main role thereof was played by positive photoresist compositions to be each used as a monolayer. The monolayer positive photoresist composition is configured to possess, in a resist resin, a frame having an etching resistance against dry etching by chlorine-based or fluorine-based gas plasma, and to possess such a resist mechanism that an exposed portion is made dissolvable, so that the exposed portion is dissolved to thereby form a pattern, and the remaining resist pattern is used as an etching mask to dry etch a processing substrate coated with the resist composition.
However, when a pattern is made finer, i.e., pattern rules are further narrowed while keeping a thickness of a used photoresist film as it is, the photoresist film is deteriorated in resolution performance. Further, when the photoresist film is to be developed by a developer to form a pattern, a so-called aspect ratio thereof is made excessively large, thereby resultingly causing a pattern collapse. Thus, the fineness has been accompanied by decrease in photoresist film thickness.
Meanwhile, although for processing of a processing substrate, there is typically used a method for processing the substrate by dry etching by adopting a patterned photoresist film as an etching mask, practically no dry etching methods exist to exhibit a complete etching selectivity between a photoresist film and a processing substrate, so that the resist film is also damaged during processing of the substrate and the resist film is collapsed, thereby failing to accurately transfer a resist pattern onto the processing substrate. Thus, with finer patterns, resist compositions have been required to have higher dry etching resistances.
Further, since shortened wavelengths of exposure have demanded that resins having lower light absorption at exposure wavelengths are used for photoresist compositions, such resins have been subjected to a transitional history from a novolak resin, through polyhydroxystyrene, and to a resin having an aliphatic polycyclic frame, commensurately with a transitional history from i-beam, through KrF, and to ArF. However, etching speeds under the dry etching condition have been practically made higher, so that recent photoresist compositions having higher resolutions practically tend to be rather lowered in etching resistance.
This kind of thing inevitably obliges a processing substrate to be dry etched by a photoresist film which is thinner and weaker in etching resistance, thereby making it urgent to ensure a material and a process in this processing state.
As one method to solve such a problem, multi-layer resist process have been used. The methods are configured to: interpose an intermediate film having an etching selectivity different from that of a photoresist film, i.e., a resist upper layer film, between the resist upper layer film and a processing substrate; obtain a pattern in the resist upper layer film; thereafter transfer the pattern to the resist intermediate film by dry etching by using the obtained resist upper layer film pattern as a dry etching mask; and further transfer the pattern onto the processing substrate by dry etching by using the obtained pattern of the intermediate film as a dry etching mask.
Several process are known as to the multilayer resist process. For example, in the case that a pattern with a high aspect ratio is formed on a substrate having steps, a two-layer resist process is known to be excellent. In this two-layer resist process, it is necessary to use a silicone polymer having a hydrophilic group such as a hydroxyl group and a carboxyl group as the resist material in order to develop a formed two-layer resist film by a generally used alkaline developer.
As the silicone-type chemically amplified positive resist used in this two-layer resist process, a silicone-type chemically amplified positive resist composition for a KrF excimer laser, for example, the composition using a base resin—obtained by protecting a part of the phenolic hydroxide group of a polyhydroxybenzyl silsesquioxane (a stable alkaline-soluble silicone polymer) by a t-Boc group—in combination with an acid generator, has been proposed (see for example, Japanese Patent Laid Open (kokai) No. H6-118651, SPIE vol. 1925 (1993) P. 377, and so on). As for an ArF excimer laser, a positive resist composition based on a type of a silsesquioxane whose cyclohexyl carboxylic acid is substituted with an acid labile group has been proposed (see for example, Japanese Patent Laid Open (kokai) No. H10-324748, Japanese Patent Laid Open (kokai) No. H11-302382, SPIE vol. 3333 (1998), and so on). As for a F2 laser, a positive resist composition based on silsesquioxane having a hexafluoro isopropanol as the soluble group has been proposed (see for example, Japanese Patent Laid Open (kokai) No. 2002-55456 and so on). The foregoing polymer contains as a main chain a polysilsesquioxane having a ladder skeleton obtained by polycondensation of trialkoxy silane or trihalogenated silane. On the other hand, as a base polymer for the resist having a silicon pendant in a side chain, a silicon-containing (meta)acrylate ester polymer has been proposed (see for example, Japanese Patent Laid Open (kokai) No. H9-110938, J. Photopolymer Sci. and Technol. Vol. 9 No. 3 (1996) p. 435-446, and so on).
As the underlayer film of a two-layer resist process, it needs to be a hydrocarbon compound that can be etched by an oxygen gas, while it needs to have a high etching resistance because it serves as a mask when a substrate thereunder is etched. In etching by an oxygen gas, it is necessary to be composed of only a hydrocarbon not containing a silicon atom. Further, in order to improve control of the line width of the upperlayer silicon-containing resist film and to reduce a concavity and a convexity of a pattern side wall formed by a standing wave and collapsing of a pattern as well, an antireflection function is also necessary; specifically the reflection rate from an underlayer film into a resist upperlayer film needs to be depressed to 1% or lower.
A three-layer process—the lamination process of forming, a resist upperlayer film of a monolayer resist not containing a silicon atom, thereunder a resist intermediate layer film containing a silicon atom, and further thereunder a resist underlayer film of an organic film—is proposed as the other multilayer resist process (see, for example, J. Vac. Sci. Technol., 16(6), November/December 1979). In general, a monolayer resist not containing a silicon atom has a higher resolution than a silicon-containing resist, and a resist having a high resolution can be used as an exposure imaging layer in a three-layer process; therefore this is suitable for a fine processing.
As the resist intermediate layer film used immediately underneath the resist upperlayer film, a CVD hard mask and a spin-on-glass (SOG) film are used. Many process for the SOG film have been proposed.
In any of the multilayer resist process, an antireflection function is necessary in order to prohibit formation of a concavity and a convexity formed by a standing wave on a pattern wall and collapsing of a pattern from occurring. For example, an optimum optical constant of the underlayer film to depress a substrate reflection in the three-layer resist process is different from that in the two-layer resist process. Although the object to depress the substrate reflection as low as possible, specifically to 1% or less, is the same in the two-layer resist process and the three-layer resist process, the antireflection effect is given only to the underlayer film in the two-layer resist process while the antireflection effect can be given to any one or both of the intermediate layer film and the underlayer film in the three-layer resist process. For example, a material for silicon-containing layer having the antireflection effect is proposed in U.S. Pat. No. 6,506,497 and U.S. Pat. No. 6,420,088. Generally, the antireflection effect is higher in the antireflection film of a multilayer than in the antireflection film of a monolayer, and thus the former is widely used industrially as the antireflection film of an optical material. Accordingly, a high antireflection effect can be expected by giving the antireflection effect to both of the resist intermediate layer film and the resist underlayer film.
Especially, because the underlayer film used in a most advanced process of semiconductor manufacturing serves as a mask at the time of forming a fine pattern by dry etching, precision pattern-transformation properties and an excellent etching selectivity are necessary. In addition, a material without deformation by an etching gas (a material without a so-called pattern deformation) during serving as a mask at the time of the etching process has been required, and thus the compounds shown in Japanese Patent Laid Open (kokai) No. 2009-14816, and so on, have been proposed. The common feature among these materials is that they have a naphthalene derivative in the main chain.
However, in a multilayer resist process, when a conventional material was used as the material to form the intermediate layer film above the underlayer film having these naphthalene skeletons, the antireflection function could not be expressed fully, thereby failed to satisfactorily depress the reflection of an exposing light. Accordingly, optimization of optical properties of a material for a silicon-containing intermediate layer film has been waited, so that it can be used most appropriately even on the underlayer film having a naphthalene skeleton.